The parallelism here articulated a kind of antithesis I don’t think we’ve seen so clearly illustrated yet: The White Lotus and The Red Lotus are opposites.
In the antebellum and war times of the ATLA timeline, the Order of the White Lotus worked in secrecy as a clandestine organization. So, when the Order’s members finally acted upon the world, their act was one of the grandest displays of power. Iroh, The Grand Lotus, and his fellow Old Masters harnessed the power of The Great Comet to effect great change.
The Red Lotus foils this. They are so advanced, so honed upon their quest for change, that even such a colossal feat as tearing down the Walls of Ba Sing Se happens for them with little effort and in virtually no time at all.
It makes such sense to me that the greatest Firebender of his age, Iroh, couldn’t accomplish this task until the arrival of the Comet, whereas an Earthbender gifted with the power to manipulate energy as a Firebender would, Ghazan, could accomplish this any day.